FEATURE
The new technology will even provide TV viewing in serious business environments such as this... which means that subscribers to the service can also receive DAB radio on their mobile phones. However, as the Virgin Mobile TV service consumes 30% of the capacity of the Digital One multiplex, in order to make way for the service the Primetime radio station was forced to withdraw from DAB last year, and three music radio stations on the Digital One multiplex were reduced to mono. A further three DAB-IP mobile TV channels could launch on Virgin Mobile next year if Channel 4 wins the licence for the new national DAB multiplex, but this would steal another 20% of the capacity of a national DAB multiplex away from its originally intended use of carrying radio. The launch of the Virgin Mobile TV service late last year should also act as a cautionary tale for those making the more inflated claims about this fledgling industry, because a £2.5m TV advertising campaign for the launch of the new service only led to 10,000 signing up. The small number of channels available and the fact that customers were forced to use a specific handset were blamed for the lack of interest. Of the other broadcast systems, Vodafone, Orange and ‘3’ participated in a trial of the MBMS standard in the Bristol area recently. One of the attractions of using MBMS for the mobile network operators is that they can transmit the service in 3G spectrum that they already own but which is separate from the 3G spectrum they’re using for voice traffic. The final system that might be used in the UK is MediaFLO, which Sky is said to favour after it trialled the system in Cambridge last year. Sky has a three-year contract for the mobile TV rights for live football
starting from next year, and it’s been reported that Sky might go it alone and launch its own mobile phone service using the lure of live football to pull the punters in. All of the broadcast systems apart from DAB-IP are using the new MPEG-4 H.264/AVC video codec (which is the same video codec as used for HDTV) and the AAC+ audio codec (which is the codec that has been adopted for the new DAB+ system). DAB-IP on the other hand uses the Windows Media Video (WMV) and Audio (WMA) codecs. Although these are all modern and efficient codecs, the picture and audio quality on the current mobile TV services is poor due to the bit rates being used for the TV channels being too low. For example, the bit rates used for the channels on Virgin Mobile’s DAB-IP service are only 88kbps combined for the video and the audio streams, whereas for good quality they should be in the region of 250–300kbps. The picture and audio quality should improve in future, though, as more spectrum becomes available for mobile TV. As well as the UHF channel 36 mentioned earlier, Ofcom will be auctioning ‘L-band’ spectrum covering frequencies 1,452 – 1,479MHz later this year, and this spectrum has been earmarked for mobile TV use across Europe. Mobile TV operators are also expected to bid for some of the spectrum that will be freed-up once analogue TV has been switched off in 2012/2013. The design of mobile phones is likely to gradually change as mobile TV becomes more popular, as many handsets that have been designed with built-in mobile TV receivers have larger displays than normal to aid TV viewing. Looking ahead, a new DVB
standard called DVB-SH (DVB – Satellite services to Handhelds) has recently been finalised, and the French company Alcatel demonstrated the new system late last year. As its name suggests, the standard has been designed for satellite transmission, with terrestrial-based ‘gap filler’ transmitters being used to cover built-up areas where the satellite signal is blocked by buildings. DVBSH is targeted at ‘S-band’ frequencies below 3 GHz, and spectrum covering 2,170 – 2,200 MHz has been earmarked for DVB-SH to use across Europe. Looking further into the future, there are already plans for an upgraded version of DVB-H, called DVB-H2, although this probably won’t see the light of day for a few years yet. South Korea is currently the leading nation in terms of mobile TV handset sales as it was the first to launch a broadcast service using its homegrown T-DMB system. But DVB-H looks like it could become the dominant mobile TV system in the years ahead, as it has already been trialled in thirty-one countries – its main competitor, T-DMB, has only been trialled in seven countries so far. Also, a nationwide DVB-H network has been launched in Italy, and national DVB-H networks are due to be launched this year in France, Germany, Spain, and Finland, and a rollout to the thirty largest cities in the US is set to begin this year as well. The UK on the other hand will have to wait until the Treasury’s palm has been greased next year before we see DVB-H...
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50 20 VHF Analogue DAB digital radio TV radio
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3G DAB L Band mobiles
Aerials have got smaller over the years as transmission wavelengths have decreased. This chart shows that DAB L Band compares with 3G.
www.hi-fiworld.co.uk
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JUNE 2007 HI-FI WORLD
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